It is necessary to provide workers with access to various work areas at the tops of rolling stock such as tank cars, which are used to transport flowing materials that typically are in liquid form but occasionally in granular form. As these tank cars are cylindrical in shape, the tops of these tank cars are curved, making for curved surfaces on which workers must maintain their balance when accessing various work areas. Though some work areas are provided with level platforms, because flowing materials are involved, even work areas with such level platforms often include slippery surfaces on which the workers must tread when carrying out their assigned duties. Various weather conditions such as rain, sleet, snow and ice also can provide and/or exacerbate slippery surfaces that can cause workers to slip and fall when carrying out their assigned duties. Thus, these work areas typically are furnished with some sort of railing structure that runs the length and width of the work area at the top of the rolling stock. However, these railing structures typically are inadequate to prevent workers from falling to the ground after slipping through one of the openings in the railing structures or tumbling over the top of the railing structures.
Before workers are permitted to access the tops of rolling stock (tank trucks, tank railroad cars, etc.), a cage can be deployed surrounding the portion of the top of the rolling stock where the workers are to be engaged in their duties. Examples of these sorts of safety cages can be found in U.S. Pat. Nos. 7,216,741, 8,479,884; 8,403,109; 8,479,882; 6,405,831; 4,679,657; 9,409,755; which are hereby incorporated herein by this reference for all purposes.
Each cage typically assumes the shape of a rectangular box having contiguous pairs of the sides connected to each other in what is essentially a right angle. In some embodiments, the corners of each cage can be curved rather than a sharp right angle. Conventionally, the cage's side that is disposed closest to the structure from which the cage is deployed will be considered the inboard side of the cage. Similarly, the cage's side that is disposed farthest away from the structure from which the cage is deployed will be considered the outboard side, One of the opposite ends of the front of the cage is connected to the inboard side while the other opposite end of the front of the cage is connected to the outboard side of the cage. Similarly, one of the opposite ends of the back of the cage is connected to the inboard side while the other opposite end of the back of the cage is connected to the outboard side of the cage.
However, as depicted in U.S. Pat. Nos. 9,133,014 and 8,051,951, which are hereby incorporated herein by this reference for all purposes, because of the presence of the railing structure, such cages remain above the top handrails and fail to provide any fall protection deployed beneath the top handrails of the railing structure. As a result, the openings beneath the top handrail can range between 22 and 30 inches and thus remain big enough for a person to slip through, thereby failing to provide adequate worker fall protection. Moreover, these cages resting on the top handrails of the railing structure typically are small (on the order of a foot tall above the handrail). Some cage structures are more elaborate and require expensive subsystems that must be activated before it is deemed safe for workers to access the work areas on the tops of the rolling railing stock. However, improper activation of these subsystems renders them less effective, and thus these subsystems require the presence of workers who are trained to operate such subsystems.
Because the railing structures atop the tanks come in a variety of different configurations, it is difficult to match the cage configuration with the railing structure in a way that ensures fall protection for the workers engaged in their duties at the particular section of the top of the rolling stock where these worker duties are to be carried out. Having to stockpile different cages with different configurations in anticipation of satisfying the requirements of many different configurations for the railing structures is so problematical as to be economically not feasible. Moreover, the worker's duties involve tasks that sometimes must be performed when the rolling stock is parked in different sorts of environments that affect the best way for these cages to be deployed to address the particular location atop the loading stock where such worker tasks are to be performed. Even so, having personnel on hand who are sufficiently competent to manipulate the cages appropriately with respect to the environments where the loading stock is parked and with respect to the configuration of the various railing structures also poses problems, Less competent personnel take longer to deploy the cages, and securing personnel sufficiently competent to deploy the cages can delay the performance of the tasks and tie up loading sites while the requisite personnel are secured. Such delays add additional cost to the performance of these tasks.
Accordingly, a need exists for apparatus that addresses these issues raised above in a manner that is uncomplicated, reliable and minimizes the need for special worker training.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate at least one presently preferred embodiment of the invention as well as some alternative embodiments. These drawings, together with the written description, serve to explain the principles of the invention but by no means are intended to be exhaustive of all of the possible manifestations of the invention.